Method of making container stock



June 15, 1965 R. T. nAvls, .JR

METHOD OF MAKING CONTAINER STOCK Filed Oct. 30, 1961 n. n y mi; tu SESSm w M #Eva N V r I F. 0 m V D f N l f E l T. A f w NT m. W mbm N .muguuw 39u R l mz3 2531i" 6 Ww nl.' Q Qk .Ibsaoklll m di ummm@ 33 3,188,734METHOD OF MAKING CONTAINER STOCK Raymond T. Davis, Jr., Monroeville,Pa., assignor to United States Steel Corporation, a corporation of NewJersey Filed Oct. 30, 1961, Ser. No. 148,514 5 Claims. (Cl. 29-528) Thisinvention relates to the manufacture of black plate or tin plate for usein the fabrication of containers and, in particular, to a method formaking plate which is protected against corrosion and discoloration, andcarries a primer or final organic coating.

Black plate and tin plate as now made are used extensively in thefabrication of containers. To permit their prolonged storage by thepurchaser prior to use, both require .chemical treatment, black platefor corrosion resistance and tin plate for discoloration resistance.Prior to fabrication into cans, furthermore, they are both lfrequentlylaquered on at least one side.

l have invented a novel method of making black plate and tin platewhereby the sheet-steel base, in the form of strip, is continuouslycoated with lacquer after initial cold-rolling to an intermediate gageand is then coldrolled to final gage with the lacquer coating thereon.The result is a product protected against corrosion anddiscoloration'and ready for fabrication into containers afterlithographing if desired, without the necessity for cleaning, chemicaltreatment or oiling after final cold-reduction.

In the present preferred practice of my method, I coldroll low-carbonsteel strip to a thickness approximating that of conventional tin plateor black plate, about 0.010", and then, after electrolytically cleaning,annealing and temper-rolling it, I coat the strip electrolytically withtin if the product desired is tin plate. I then apply to the tin plateor to black plate without tinning, if that is the desired product, acoating of lacquer on one or both sides. The lacquer-coated strip isthen passed through a lacquercuring chamber wherein it is suitablyheated and then coiled after cooling. I then cold-roll thelacquer-coated strip to a final thickness of about one half that of thestrip after coating.

A complete understanding of the invention may be obtained from thefollowing detailed description and explanation which refer to theaccompanying drawing the single figure of which is a diagramillustrating the present preferred practice.

Referring now in detail to the drawing, low-carbon steel strip S iscold-rolled to a thickness of about 0.010 (corresponding to 90 poundsper base box) in a mill 10 of known type. The strip is next passedthrough a conventional electrolytic alkaline cleaning tank 11 and thencethrough a continuous annealing furnace 12, also of known construction.After cleaning and annealing, the strip is temper-rolled in a mill 13where it is subjected to a reduction of only from 1 to 6%.

If the final product desired is tin plate, the strip is next passedthrough a continuous electrolytic tinning line 14, of known type.Thereafter, the strip is passed through a lacquer-coating line l5. Ifblack plate is to be the final product, the tinning line is by-passedand the strip is sent from mill 13 directly to the lacquer-coating line.

In the line 15, the strip S is uncoiled and passed through aconventional roller coater 16 which applies a film of lacquer over theentire surface of one or both sides of the strip. The lacquer vappliedmay be of any suitable type, vexamples of whichl are that made byWatson-Standard after curing but before further cold reduction,of from i4 to 1l mg./sq.in., conveniently about 7 mg./sq.in. After coating, thestrip is passed through a heating chamber 17 where it is heated to atemperature from about 375 to i' It is then cooled by contact with theatmos- 420 F. phere on emerging from chamber 17 and recoiled.

The lacquer-coated strip is next cold-rolled to effect' about a 50%reduction in its thickness, i.e., from about A 0.010 to about 0.005(corresponding to 45 pounds per 3,188,734 Patented June l5, 1965 i basebox), by one or more passes through a reducing stand or stands 18, inaccordance with usual coldrolling practice. In this rolling, both thelacquer coatings and the base metal are reduced simultaneously inthickness` but the coatings are not damaged nor is their adherenceimpaired. The finished product has a continuous uniform coating oflacquer strongly adherent thereto. The coating weight, of course, isreduced in proportion to the reduction in metal thickness but therolling of the lacquercoated strip presents no problem either offragmentation of the coating or adherence thereof to the rolls. Theproduct is well suited as such for fabrication into containersimmediately or after further lacquering and lithographing if desired.

The advantages of my method are the economies in manufacture resultingtherefrom. As stated, the conventional cleaning subsequent to finalcold-rolling is made unnecsary, and the chemical treatment and oilingmay be avoided in the production of tin plate. The chemical treatment isalso eliminated from the operations which have been required in themanufacture of black plate. The lacquer coating, of course, protectsblack plate from l' corrosion and tin plate from discoloration andabrasion.

The efiiciency of the use of lacquer is increased, since the amount oflacquer which has been used heretofore covers twice as great an area ofproduct, either tin plate or black plate.

Although I have disclosed herein the preferred practice.

than that desired in the finished product, applying a lacquer coating tothe strip, thermally curing the lacquer coating, and cold-rolling thelacquer-coated strip thereby reducing its thickness to final gage.

2. A method as defined in claim 1, characterized by applying saidcoating in a thickness such as to result in a I coating weight of from 4to 10 mg. per square inch on one side only.

3. A method as defined in claim 1, characterized by applying saidcoating to both sides of said strip.

4. A method as defined in .claim 1, characterized by reducing said stripby said first cold-rolling to a thicknessA of about 0.010" and by saidsecond cold-rolling to a.;

thickness of about.0.005".

5. A method of making lacquered steel strip comprising cold-rollingstrip to intermediate gage, lacquering the strip, then cold-rolling itto final gage and effecting a substantial reduction in the striprolling.

' References Cited by the Examiner UNITED STATES PATENTS 1 ,898,739

3,110,413 11/63 McKay et al. 29-528 X WHI'IMORE A. WILTZ, PrimaryExaminer. HYLAND Blzor, Examiner.

thickness by said final cold- 2/33 Meyer 29-521 XA f 2,850,999 9/58Kaplan et al. 29-528 X

1. A METHOD OF MAKING CONTAINER STOCK COMPRISING COLD-ROLLING LOW-CARBONSTEEL STRIP TO A THICKNESS GREATER THAN THAT DESIRED IN THE FINISHEDPRODUCT, APPLYING A LACQUER COATING TO THE STRIP, THERMALLY CURING THELACQUER COATING, AND COLD-ROLLIONG THE LACQUER-COATED STRIP THEREBYREDUCING ITS THICKNESS TO FINAL GAGE.